In recent years, with the gradual improvement of the luminous efficiency of LED and the gradual decrease of cost, semi-conductor lighting gradually becomes the development trend of modern lighting, which is recognized as the fourth generation of lighting source after incandescent lamp, fluorescent lamp, and energy-saving lamp, thus called “green lighting in 21st century.”
To apply the semiconductor lighting to the normal lighting field, it is necessary to obtain the high efficient and high color rendering white-light LED. Now, there are several ways to achieve the white-light LED, and the most important way is to apply a yellow phosphor (YAG) on a blue-light LED chip, thereby realizing white-light emission. However, this way has the drawbacks of high coloring temperature and low color rendering index, and thus it cannot satisfy the demands of semi-conductor lighting. Although the emission spectrum of YAG phosphor is very wide, the emission intensity within the red-light area is rather weak, and the phenomenon of red-light deficiency occurs after being mixed with the blue-light LED chip, which therefore affects the relevant color temperature and color rendering index of the white-light LED. Thus, the YAG itself cannot solve the existing problem. However, the above problem can be solved by adding red phosphor.
However, the red phosphor is always one of significant bottlenecks that restrict the technical development of white-light LED. The currently red phosphor has various kinds of problems, for example, CaS:Eu2+ having large luminous attenuation and poor chemical stability, CaMoO4:Eu2+ having narrow excitation scope, Y2O3:Eu2+ and Y2O2S:Eu2+ having low luminous efficiency, and M2Si5N8:Eu2+ having a poor anti-luminous attenuation performance, none of which can match perfectly with the LED chip.
The U.S. Pat. No. 7,252,788 discloses a nitride phosphor comprising MmAaBbNn:Zz, where M is a divalent element selected from at least one of Be, Mg, Ca, Sr, Ba, Zn, Cd and Hg; A is a trivalent element selected from at least one of B, Al, Ga, In, Tl, Y, Sc, P, As, Sb and Bi; B is a quadrivalent element selected from at least one of C, Si, Ge, Sn, Ti, Hf, Mo, W, Cr, Pb and Zr; and Z is an activator selected from at least one of rare earth element or transition element; (m+z):a:b:n=1:1:1:3, 0.0001≦z/(m+z)≦0.5. The phosphor may be effectively excited between 300-550 nm, and the position of emission peak varies with the content of Eu2+. The manufacturing method uses one-step synthesis method. The synthesis temperature is 1200-1700° C.; the pressure is about 0.5 Mpa. The family of this patent comprises: JP2005239985, EP1568753, and CN1683470A.
The U.S. Pat. No. 7,273,568 discloses a phosphor with the formula of MmAaBbOoNn:Zz, where M is a divalent element selected from at least one of Mg, Ca, Sr, Ba and Zn; A is a trivalent element selected from at least one of B, Al and Ga; B is a quadrivalent element selected from Si or Ge; and Z is an activator selected from at least one of rare earth element or transition element. The manufacturing method also uses one-step synthesis method. The pressure is 0.001 MPa≦P≦0.1 Mpa. Similar patents include U.S. Pat. No. 7,476,337, U.S. Pat. No. 7,476,338, and EP1630219, etc.
The US patent US2010096592 discloses a phosphor comprising M-Al—Si—N, where M is Ca, Sr, and Ba, and adds LiF as flux.
The manufacture method of all the existing patents uses the high-temperature and high-pressure one-step synthesis method. However, the resulting phosphor has relatively low luminous intensity. Furthermore, this manufacturing method is quite demanding on the devices. Therefore, they have problems such as high cost and complex process.